Cutting die system

ABSTRACT

SEVERAL DIE UNITS FOR SIMULTANEOUSLY CUTTING MULTIPLE PORTIONS OF FLAT MATERIAL ARE MOUNTED ON A BACKER PLATE WITH DOUBLE HEADED SMOOTH PINS WHICH ENGAGE SMOOTH PERFORATIONS OF BRACKETS FASTENED AT BALANCE POINTS TO BLADE SECTIONS OF THE INDIVIDUAL DIE UNITS, AND CORRESPONDING SMOOTH PERFORATIONS OF THE BACKER PLATE. ELASTIC GROMMETS WITH ELONGATE HOLES AND TABS ARE INSERTED BETWEEN BACKER PLATE AND BRACKET, AND BETWEEN BRACKET AND INNER PIN HEAD, THE OUTER PIN HEAD RESTING IN A COUNTERBORE OF THE FREE SIDE OF THE BACKER PLATE. THE BACK EDGE OF THE BLADES ARE DISTANCED FROM THE BACKER PLATE. IN A MODIFICATION, A SINGLE DIE UNIT IS FASTENED TO A BACKER PLATE WITH THE SAME TYPE OF DOUBLE HEADED SMOOTH PINS, BUT ONLY ONE GOMMET BETWEEN BRACKET AND INNER PIN HEAD AND WITH THE BACK EDGE OF THE BLADE RESTING ON THE PLATE.

NOV. 2, 1971 LARSON 3,616,120

CUTTING DIE SYSTEM Filed Aug. 20, 1969 @1 mll' M 7 L. ILM

Y I K, 7 g IQaIJiZ ZZ-Qf United States Patent 3,616,720 CUTTING DIE SYSTEM Robert A. Larson, Norwell, Mass, assignor to Boston Cutting Die Company, Dorchester, Mass. Filed Aug. 20, 1969, Ser. No. 851,675 Int. Cl. 1326f 1/44 US. Cl. 83691 6 Claims ABSTRACT OF THE DISCLOSURE Several die units for simultaneously cutting multiple portions of flat material are mounted on a backer plate with double headed smooth pins which engage smooth perforations of brackets fastened at balance points to blade sections of the individual die units, and corresponding smooth perforations of the backer plate. Elastic grommets with elongate holes and tabs are inserted between backer plate and bracket, and between bracket and inner pin head, the outer pin head resting in a counterbore of the free side of the backer plate. The back edge of the blades are distanced from the backer plate.

In a modification, a single die unit is fastened to a backer plate with the same type of double headed smooth pins, but only one grommet between bracket and inner pin head and with the back edge of the blade resting on the plate.

BACKGROUND OF THE INVENTION Field of the invention The invention relates to the art of cutting work pieces from flat material, and particularly to mounting of several dies on a common support for simultaneously severing individual portions of material.

DESCRIPTION OF THE PRIOR ART For die cutting several pieces of material in a single economical operation, various systems of multiple dies have been proposed. These known systems have various drawbacks, among others the unsolved problem of securely fastening several dies of different shapes close together so that a minimum of material will be wasted, while being able to break the die units apart with a minimum of effort such that units can be taken away or added after a sufficient number of pieces of a particular shape have been cut to satisfy production requirements.

A basic design commonly in use is to place die units or contours in their required positions with a minimum of waste spaced on a rigid support and then to weld these units to each other and to the support, forming one rigid piece. This has various disadvantages such as the necessity of breaking up the entire assembly if one unit is damaged and needs repair, and also the necessity of placing the units close to one another; if the individual die units are too close to each other the material being out eventually becomes jammed into the narrow areas between the rigidly related die contours causing pressure on the blades and ultimately breaking the units apart.

It has also been proposed to mount the individual die cavity or contour units on a backer plate instead of welding them into one solid piece with or without a common support; the individual units are usually mounted on a backer plate by means of screws reaching through braces in the die units into the backer plate. This technique permits the fairly easy removal of a die unit if should become damaged during production which can even continue With the remaining die units. However, the situation of die cavities placed rigidly close together remains and the cut material still causes die breakage because of Patented Nov. 2, 1971 the unyielding spaces between the die contours which tend to retain jammed waste material.

In order to overcome these defects, it has further been proposed to mount the individual die units floatingly by mounting them on a backer plate by providing each unit with cross braces which are screwed to a backer plate, with elastic grommets between braces and plate. This system is described in Pat. No. 3,373,643 of Mar. 19,. 1968 to E. M. Spengler. This construction allows some degree of movement between the units within the whole assembly of cavities mounted on the back plate, thus providing slight lateral movement during the cutting process and alleviating the problem of jamming between the units with consequent die breakage. Also, the die units can be placed closer together than in the rigidly joined assemblies mentioned above. Nevertheless, Spenglers system suffers from several inherent weaknesses. One is the use of screws threaded into the backer plate which makes it difficult to remove the die unit and to relocate and change the die contours to fit production requirements. The second disadvantage is caused by the cross brace system taking up considerable room within the individual die cavities, thus reducing the overall cutting depths available. A typical cutting die height commonly used in the industry is about 1 /4". To accommodate the cross braces of the Spengler system it is necessary to use a backer plate at least thick to allow enough thread for the screws, which leaves a possible die height of only 1%. This height is further restricted by one or more cross braces, the rubber grommets and the screws for each unit which together take up approximately 50% of the usable cutting height of the die cavities. A third disadvantage of the Spengler system is the sheer bulk of the components including cross braces and screws, which renders this die assembly unnecessarily heavy and tiring for a machine operator. Thus, the usefulness of the cutting process is not wholly satisfactory in spite of the fioating die mounting.

The present invention basically minimizes the weight problem, maximizes the usable cutting depth within each cutting cavity and, of particular importance permits the quick tearing down and fast setup of new configurations of die contour units.

SUMMARY OF THE INVENTION In its principal aspect the invention is characterized by a plurality of cutting blade units, each of which has brackets on the inside of the contour sections. The brackets are fastened to the die blades, such as by riveting, preferably at the balance point of the respective die section and extending towards the inside with a smoothly perforated portion. A backer plate has smooth perforations corresponding to those of the brackets. Brackets and backer plate are connected by means of smooth pins with two heads, one head being capable of passing through both, bracket and back plate perforations, and the second head being larger than the back plate perforation such that the first head of the pin can be inserted through the back plate and the bracket, with the second head resting on the back plate. Elastic grommets are inserted between the back plate and the adjacent side of the inwardly extending bracket portion, and between the other side of that bracket portion and the second, smaller pin head. The usually dull edge of the die blade, opposite the cutting edge, is preferably distanced from the backer plate wherever it comes within the contour of the latter. In a preferred embodiment, the grommets have an oval perforation and a tab, which provisions permit particularly easy insertion on the pins.

In a modification, only one grommet is used, between the bracket and the second, smaller head, the other brack et side resting directly on the back plate. In this embodiment, the dull edge of the die blade can rest on the backing plate or be distanced therefrom as in the first embodiment.

Objects of the invention are to provide a multiple cutting die system which utilizes a simple mounting expedient permitting optimal quick assembly without tools; which has an improved floating effect due to individual elastic bodies such as grommets on sections of the die units which permit relative movement of the units, and of the sections within a unit, with minimal obstruction and hence maximal cutting space within each die cavity; which has optimal internal height of the die unit assembly; which allows instant removal of any die unit which might become damaged or break during production, with a minimal effort and without using any tools; which permits the use of preground, pretempered and presharpened thin wall die stock by eliminating cross braces between die sections and by avoiding heating of the pretempered stock for joining the brackets; and which system permits the manufacture of dies in any height required by various cutting situations with either inside, outside or center bevel of easily available die stock.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is the top view of a composite die according to the invention;

FIG. 2 is a section on 22 of FIG. 1;

FIG. 3 is the elevation of a pin according to the invention;

FIG. 4 is an isometric view of the general shape of grommets according to the invention;

FIG. 5 is a view of a modified grommet of preferred shape according to the invention;

FIG. 6 is a diagram indicating the relation between the oval hole of a grommet according to FIG. 5 and a pin according to FIG. 3;

FIG. 7 is a section on 7-7 of FIG. 2; and

FIG. 8 is a section similar to FIG. 2, of a modified single die assembly according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIGS. 1 and 2, a hacker plate 11 is cut with an outline approximately conforming to the component contour of the assembled individual die units 21, 22, 23, 24. It will be evident that the outline of the back plate does not have to coincide with the outer contour of the assembled units, and that any required number of units can be built up to a die according to the invention. The plate 11 has smooth bores as indicated at 12 in FIG. 2 for one bracket. Each bore 12 is counterbored at 15. The distribution of the smooth bores in the back plate 11 is determined by the configuration of the component die units as will appear hereinbelow.

Each individual die unit 21, 22, 23, 24 consists of a blade as indicated at 31 for unit 21, which has a certain number of sections, in the present case for unit 21, three sections 41, 42, 43. To the balance point of each section, for practical purpose the midpoint between the corners, are fastened mounting brackets 45, 46, 47 of angular shape, each with two legs 45.1 and 45.2 as shown in FIG. 2. The blade legs 45.1 are fastened to the respective sections at holes 48.1, and perforations 48.2, two for each bracket. Rivets such as 49 are preferred for that purpose, in order to avoid heating of the tempered blades, but it will be understood that instead of riveting the brackets can be fastened to the blades by other means such as by screws, or welding if heating is of no consequence. As shown in FIG. 2, the leg 45.2 has a smooth perforation which is larger than the inner head as will be described herein below. Both sides of the bracket arm 45.2 are roughened such as by an abrasive finish, in order to restrict the movement of the mounting bracket between the elastic grommets, as indicated at 45.3.

The pins, one for each bracket and blade section as indicated at 61, 62, '63, of FIG. 1, have a smooth shank 65 (FIGS. 2 and 3), a large head 66 and a smaller head 67. The smaller head 67 is dimensioned to pass through the hole 12 of the plate 11 as well as through the perforation 49 of the bracket leg 45.2. The larger head 66 is dimensioned not to pass through the hole 12 through which the head 67 will pass. The head 66 rests in the counterbore 15 of the back plate.

The two grommets 71, 72 for each bracket and pin are generally speaking shaped as indicated in FIG. 4, with a hole 73 and a tab 74. The hole 73 is somewhat smaller than the smooth shank 65 of the pin and the outside diameter of the grommet proper is somewhat smaller than the contour of the bracket legs 45.2. A preferred embodiment of the grommet is shown in FIG. 5. It was found that an elongate hole 75 promotes easy insertion of the grommet over the head 67 of the pin. The dimensions of this preferred embodiment are indicated at a, b, c, d, e, as follows:

These grommet dimensions are satisfactory for pins. In a preferred embodiment, the larger pin heads 66 are stepped with a larger portion 66.1 contacting the counterbore bottom, and the smaller portion 66.2 fitting the bore. FIG. 6 indicates the preferred relation of grommet and pin shanks, the pin shank being indicated in dotted lines at 65 and the elongate hole 75 in the shape before insertion on 65 when it will approximately conform to the shape of 65, as indicated in FIG. 7.

As customary, a stripper body 50 is inserted in the cavity of each die unit, as indicated in FIG. 2. The strippers are made from sponge rubber or similar material and serve to eject the die cut material from the die cavities.

The combination dies according to the invention are assembled as follows. The individual blade units are first fabricated from pre-ground, pre-tempered and presharpened thin wall rule die stock of any required height. Either inside, outside or center level die stock can be used. The blades are heated at the sharp bends or corners required by their configuration, just enough to prevent breaking. After bending to shape, the blades are quenched to restore the temper. Closed shapes are obtained by welding at one corner, again with subsequent quenching. The blades are then drilled or punched at the balance points of their sections for the rivets 49 and the brackets riveted thereto. The units are then placed as desired on the backer plate usually from aluminum, and the holes and plate marked with a contour configuration appropriate to fit into a die press. The holes for the pins are then drilled and countersunk and the backer plate cut to the marked configuration. The pins are then inserted with heads 67 passing through holes 12 into the counterbores, and the first grommets 71 applied. The blade brackets are then inserted with the smaller heads 67 passing through the holes 49. The second grommets 72 are then forced over the heads 67 which, similar to the insertion of grommet 71, is facilitated by the tabs 74 and elongate holes 75 of the grommets. The thickness of the grommets is such that the brackets and therefore their blades are firmly and yet slightly yieldingly held on the hacker plate 11 by the compression of the grommets. The roughening 45.3 of the bracket arms 45.2 prevents slippage between the bracket arm and the grommets, making the elasticity of the grommets effective only within their own bodies.

For disassembling a composite die of this type, it is only necessary to pull the upper grommets 72 by their tabs over the smaller pin heads 67 and to remove the brackets of the units by slipping the small heads through the bracket holes 49. The inner grommets 71 can then be pulled on their tabs over the heads 67.

DESCRIPTION OF A SECOND EMBODIMENT It was found that the above described floating construction with brackets, smooth pins, and elastic grommets adapts itself well for applications where quick and convenient assembly is primarily required rather than floating movement between the die units of an assembly on a backer plate. Such an application is the mounting of a single die unit on a backer-plate, where yielding of individual die units is irrelevant. This modification will now be described.

In FIG. 8, a backer plate 111 is cut to conform approximately to the counter of a single dies unit with blade 13 1 that rests directly, with friction, on the plate. Brackets 141, similar to those described with reference to FIGS. 1 and 2 are riveted to the blade at its section balance points with two rivets 49 for each bracket, the leg 145.2 flush with the dull edge of the blade. The pin 16 5 is similar to pin 65 as above described, but shorter, such as to provide sulficient compression for the single grommet 171 which is identical with that according to FIG. 5.

The assembly is similar to that outlined above for a floating die unit assembly. The back of the blade and the legs 145.2 are set flush on the plate 111, the pins 165, one for each section of the die unit, are inserted with the smaller head through the hole of the leg, and the grommets 171 are then snubbed on. The surface 145.3 is preferably roughened, similar to the surfaces 45.3 of FIG. 2. A stripper 150, corresponding to the above-described strippers 50, is inserted into the die cavity.

It will now be evident that, while the brackets and blades are rigidly connected to the backer plate, various advantages of the principal embodiment are obtained with the second embodiment, such as quick mounting without tools, and increased internal height of the die.

I claim:

1. A cutting die comprising:

a plurality of die units each having a blade with a cutting edge, a back edge and two sides, each unit being in the shape of a polygon defined by blade sections;

a backer plate having smooth perforations which conform to the cutting patterns of respective units;

a plurality of mounting brackets each having a mounting flat and inclined at right angles thereto a holding portion with two opposite roughened faces, said flats being riveted to the balance points of said blade sections and each of said holding portions having a smooth perforation;

a plurality of smooth pins each having a smooth shank, a first head capable of passing through both bracket and backer plate perforations and a second head larger than said backer plate perforations, the pins extending through backer plate and bracket perforations with the first head extending through and beyond said bracket perforations and with the second head resting on the back plate on the side opposite the brackets; and

two elastic grommets for each pin having tabs and oval perforations whose lesser diameters are in relaxed condition smaller than said pin shanks and which embrace respective pin shanks under compression between said holding portions of the brackets and said first pin head, and between said back plate and said holding portions such as to distance said back edge of the strip means from the backer plate;

whereby the grommets floatingly secure the die units to the backer plate.

2. A cutting die comprising:

die unit means with blade means outlining a unit cutting pattern and having a cutting edge, a back edge and two sides;

backer plate means having perforations conforming to the unit cutting patterns;

a plurality of mounting bracket means, each having a mounting flat, and inclined there to a holding portion with two opposite roughened faces, said flats being fixed to one of said sides of the blade means and said holding portions having a perforation;

a plurality of pin means each having a shank, a first head capable of passing through both bracket means and backer plate perforations and a second head larger than said backer plate perforations, the pin means extending through backer plate means and bracket means perforations with the first head extending through and beyond said bracket means perforations and with the second head resting on the backer plate on the side opposite the bracket means; and

elastic grommet means for such pin means having perforations embracing the shanks of respective pin means under compression between said holding portions of the bracket means and said first pin head, whereby the grommet means secures the blade means to the hacker plate means;

said grommet means including single grommets located between the adjacent faces of said holding portions and said first pin heads.

3. A cutting die according to claim 2, wherein said grommet means includes a first grommet located between one of said faces of the holding portion and said first pin head, and a second grommet between said back plate means and the second face of the holding portion holding the back edge of the blade means spaced from and movable relative to the back of the plate whereby the blade means are floatingly secured to the backer plate means.

4. A cutting die according to claim 2, wherein the backer plate perforation is countersunk at the side opposite the bracket means and said second pin means head is stepped with the smaller diameter portion centering the pin in the smaller perforation of the countersunk backer plate means and with the larger diameter portion resting against the countersunk face of the backer plate means perforation.

5. A cutting die according to claim 2, wherein said grommets have peripheral tabs facilitating insertion of the grommets over the pin heads.

6. A cutting die according to claim 2, wherein said perforations of the grommet means are oval with the lesser dimension smaller than the diameter of the pin shank between the pin heads.

References Cited UNITED STATES PATENTS 576,023 1/1897 Bosworth a 83-691 2,313,801 3/1943 Carll 83691 2,367,657 1/1945 Boersma 29-450 UX 3,053,046 9/1965 Fleming, Jr. 29 450 UX 3,373,643 3/1968 Spengler 83-620 3,529,506 9/1970 Malm et a1 83-698 JAMES M. MEISTER, Primary Examiner U.S. Cl. X.R. 

